A palladium catalyst comprised of a phosphorous compound and a palladium compound is useful as a catalyst for a telomerization reaction between two conjugated alkadiene molecules and a nucleophilic reactant. Specifically, it is useful as a catalyst for production of 2,7-octadien-1-ol by reacting two butadiene molecules with one water molecule in the presence of carbon dioxide and a tertiary amine to perform a telomerization reaction. 7-Octenal can be derived from 2,7-octadien-1-ol thus obtained by an isomerization reaction and 1,9-nonanedial can be derived from 7-octenal by a hydroformylation reaction. From the viewpoint that 1,9-nonanediamine which is useful as a raw material for a monomer for a polymer can be derived from 1,9-nonanedial by a reductive amination reaction, the 2,7-octadien-1-ol is of a high industrial value, and it is therefore important to develop a catalyst advantageous for the production thereof.
In order to produce 2,7-octadien-1-ol in an industrially advantageous manner, it is preferable to recover palladium as a noble metal in the telomerization reaction and reuse it in the reaction. As such a method for producing 2,7-octadien-1-ol, there are two methods using a telomerization reaction, as followings:
(A) a method for producing 2,7-octadien-1-ol, in which butadiene and water are subjected to a telomerization reaction in the presence of a palladium catalyst comprised of a palladium compound and a water-soluble phosphine in an aqueous sulfolane solution including a carbonate of a tertiary amine and a bicarbonate of a tertiary amine to generate 2,7-octadien-1-ol, in which at least part of the reaction mixed liquid is extracted with a saturated aliphatic hydrocarbon or the like to separate out the 2,7-octadien-1-ol by extraction, and at least a part of the sulfolane eluent including the palladium catalyst is recycled and used in the reaction (see PTLs 1 to 3), and
(B) a method for producing 2,7-octadien-1-ol, in which a tertiary amine having a function as a surfactant capable of compensating for a low reaction rate due to low solubility of butadiene in water coexists therewith in a two-phase system including an aqueous phase having a palladium catalyst comprised of a palladium compound and a water-soluble phosphorus-containing compound dissolved in water and an organic phase which is butadiene, and then butadiene and water are subjected to a telomerization reaction (see PTL 4 and NPL 1).
In the method (A), 2,7-octadien-1-ol is extracted by adding a saturated aliphatic hydrocarbon to a telomerization reaction liquid, and it is thus necessary to install equipment for distillation and recovery of the saturated aliphatic hydrocarbon, which results in an increase in cost burden associated with the equipment. Further, sulfolane is more expensive than ordinary hydrocarbon-based solvents, such as hexane, and accordingly, it is necessary to recover the sulfolane by subjecting the 2,7-octadien-1-ol phase obtained by extraction to washing with water, or the like. In addition, since sulfolane is a sulphur atom-containing substance, in a case of incineration disposal of sulfolane, an incinerator having desulphurization equipment is required. Therefore, there is a demand for a method for conveniently recovering most of a palladium catalyst after a telomerization reaction while not using sulfolane in the telomerization reaction.
In the method (B), dimethyldodecylamine, for example, is used as a tertiary amine. Since the dimethyldodecylamine has a function as a surfactant, complicated operations such as multiple extraction and recovery, or distillation and separation are required so as to increase the recovery of a tertiary amine. Further, according to Examples, it can be said that the method (B) is a method having low selectivity for 2,7-octadien-1-ol. Therefore, there is also a demand for a method in which the tertiary amine to be easily recovered can be used, and the selectivity for 2,7-octadien-1-ol is high.
Moreover, as a method for producing a water-soluble triarylphosphine which can be used in a telomerization reaction, the following methods are known:
(1) a method for producing a bis(3-sulphonatophenyl)phenylphosphine disodium salt, by dissolving triphenylphosphine in sulphuric acid, and then reacting the solution with sulphur trioxide in fuming sulphuric acid (see NPLs 2 and 3),
(2) a method for producing a bis(3-sulphonatophenyl)phenylphosphine disodium salt by sulphonation of triphenylphosphine using an anhydrous mixture of sulphuric acid and orthoboric acid (see PTL 5),
(3) a method in which triarylphosphine having an electron donating group such as a methyl group and a methoxy group in an aromatic ring is reacted with sulphur trioxide in the presence of sulphuric acid (see NPL 4), and
(4) a method in which triarylphosphine having an electron donating group such as a methyl group and a methoxy group in each of three aromatic rings is reacted with sulphur trioxide in the presence of sulphuric acid (see NPL 5).
In the case of using the alkali metal salt of a triarylphosphine having a sulphonate group, obtained by these methods, in a telomerization reaction, there is a problem in that inorganic salts such as hydrogen carbonate of an alkali metal are accumulated in the reaction system, thus blocking pipes. It is known that as a method to avoid this problem, it is preferable to use an ammonium salt obtained by reacting a triarylphosphine having a sulphonate group with a tertiary amine as a catalyst for a telomerization reaction (see PTL 6).
In the method (1) for producing a water-soluble triarylphosphine, a bis(3-sulphonatophenyl)phenylphosphine disodium salt can be produced by sulphonating triphenylphosphine having a benzene ring as an equivalent aromatic ring relative to one phosphorus atom bonded thereto with sulphur trioxide, followed by neutralization with sodium hydroxide, but the yield is as low as 60%. This is mainly caused by by-production of a tris(3-sulphonatophenyl)phosphine trisodium salt, indicating that it is difficult to selectively introduce only “two” sulpho groups with respect to the equivalent aromatic ring.
The method (2) for producing a water-soluble triarylphosphine is a method in which orthoboric acid is used instead of sulphur trioxide during a sulphonation reaction. The bis(3-sulphonatophenyl)phenylphosphine disodium salt is acquired with a yield of 94%, but in order to remove boric acid completely, toluene and triisooctylamine are added to a sulphonation reaction liquid once to cause a desired amine salt to be present in an organic phase, the organic phase is sufficiently washed with water, and the aqueous phase obtained by adding an aqueous sodium hydroxide solution to the washed organic phase is neutralized with sulphuric acid, and then concentrated. Then, methanol is added thereto to obtain a supernatant, from which methanol is removed, thereby acquiring a bis(3-sulphonatophenyl)phenylphosphine disodium salt. Although the yield is high, it is necessary to repeat washing to remove boric acid. Therefore, this method is difficult to carry out industrially.
The method (3) for producing a water-soluble triarylphosphine is a method in which a triarylphosphine in which an electron donating group such as a methyl group and a methoxy group is introduced in advance to an aromatic ring is reacted with sulphur trioxide in the presence of sulphuric acid. Bis(4-methoxyphenyl)phenylphosphine having a non-equivalent aromatic ring, or the like is used as a raw material to acquire bis(4-methoxy-3-sulphonatophenyl)phenylphosphine disodium salt with a yield of 85%. Further, it can be shown that in the method (4) for producing a water-soluble triarylphosphine, a bis(6-methyl-3-sulphonatophenyl)(3-sulphonatophenyl)phosphine trisodium salt can be produced with a yield of 21% from bis(2-methylphenyl)phenylphosphine. However, from the viewpoint that the bis(2-methylphenyl)phenylphosphine used in the present invention has a small number of substituents such as a methyl group, as compared with bis(2,4-dimethylphenyl)phenylphosphine, the number of sulpho groups or sulphonate groups introduced tends to be 3, and therefore, there is a concern that the yield of a desired bis(6-methyl-3-sulphophenyl)phenylphosphine, and in addition, the yield of the bis(6-methyl-3-sulphonatophenyl)phenylphosphine diammonium salt will be lowered.
As a method for producing an ammonium salt of a triarylphosphine having a sulphonate group, methods in which for an alkali metal salt of a triarylphosphine having a sulphonate group is used as a raw material, a counter-cation is converted into a desired ammonium salt by an ion exchange process in the following manner are known. The methods are as follows:
a method in which sulphuric acid is added to an aqueous solution of a diphenyl(3-sulphonatophenyl)phosphine sodium salt, 4-methyl-2-pentanone is then added thereto, and triethylamine is added to the obtained organic phase, thereby precipitating a solid-state diphenyl(3-sulphonatophenyl)phosphine triethylammonium salt (see PTL 6); and
a method in which a diphenyl(3-sulphonatophenyl)phosphine sodium salt is pressurized with carbon dioxide in the presence of triethylamine, ethanol, and 2-propanol to acquire a desired product from a filtrate of the reaction liquid (see PTL 7).